The present embodiments relate to computer networks and are more particularly directed to a method and apparatus to map network packet behaviors from one architectural model layer to another architectural model layer.
An architectural model provides a common frame of reference for discussing communications along a computer network, and it separates the functions performed along the network into different layers stacked on top of one another. Each layer provides a predefined interface to the layer above it. For example, the Open Systems Interconnection (“OSI”) reference model has seven layers, typically defined as shown in the following Table 1:
TABLE 1LayerFunction7.ApplicationEnd user services provide by application programs,such as web browsing, e-mail, audio and video6.PresentationStandardizes data presentation to the applications, suchas handling data syntax, problems, and datacompression5.SessionManages session between nodes and manage data flowfrom higher layers to the lower layers, includingtiming and buffer management when multipleapplications attempt data transmission at a same time4.TransportProvides end-to-end delivery of packet, such asthrough error detection and correction3.NetworkRoutes each packet across a given network2.Data LinkTransmits and receives packets through the physicallink1.PhysicalProvides the cable or physical characteristic of thenetwork mediaAs another example, the transmission control protocol (“TCP”)/internet control protocol (“IP”), referred to as TCP/IP, reference model is sometimes described using three to five layers, and most commonly as having four layers. These four layers typically are defined as shown in the following Table 2:
TABLE 2LayerFunction5.ApplicationGenerally provides the functions of layers 5 through 7of the ISO/OSI model4.TransportProvides end-to-end delivery of packet, such asthrough error detection and correction3.InternetworkRoutes each packet across a given network and definesa the datagram2.LinkAccesses physical network, such as through kerneloperating system and device driver interfacesWithin a network, the layered approach permits design such that each layer at a given node can communicate with the same layer at another node and, more particularly, each layer protocol at one node can communicate with a peer protocol in the equivalent layer at another node. Theoretically, one layer does not care about the layer(s) above or below it, although there is a dependency in that every layer is involved in sending data from a local application to an equivalent remote application. Thus, the layers are required to have a manner of passing data between themselves on a single node and the upper layers rely on the lower layers to communicate data to the underlying network.
Given the preceding, it is recognized in the present industry that newer techniques are preferable for improving data flow along a network, and one such technique is referred to as quality of service (“QoS”). QoS has become increasingly a focus due to the larger demands from certain applications in combination with the ever-increasing size and complexity of the global internet. In the past, network communications were sometimes attempted or achieved using ordinary “best effort” protocols. However, for applications such as high-bandwidth video and multimedia, transmitting the data from such applications along a network in a reliable and satisfactory manner has proven difficult. QoS is therefore used with such applications so that transmission rates, error rates, and other characteristics can be measured, improved, and, to some extent, guaranteed in advance. Using various mechanisms, such as the global internet's Resource Reservation Protocol (“RSVP”) and asynchronous transfer mode (“ATM”), packets can be expedited based on criteria determined in advance or a set of QoS can be pre-selected and guaranteed in terms of certain parameters such as average delay, delay variation, cell losses, and the transmission error rate.
QoS is currently implemented in layer 3 of TCP/IP networks in connection with two types of services, namely, integrated services and differentiated services. Integrated services relate to a single network flow, where a flow is commonly defined as a session of packets from a single source node to one destination node (and possibly others), where the flow is sometimes also recognized by having an actual flow identifier in the packet or it may be identified by various indicators such as when using ATM. QoS is presently achieved for integrated services using the RSVP to reserve resources in advance of transmitting the flow packets. Note, however, that QoS for integrated services is limited in that in a big network there may be millions of resources, so it is not feasible to scale the resource reservation across the entirety of the network. Differentiated services is a protocol that may apply to multiple flows, as opposed to the single flow nature of integrated services. Differentiated services presently are categorized by a six-bit control field known as a differentiated services control point (“DSCP”), where the DSCP is a field in each packet and can relate to multiple flows that each have an attribute that gives rise to a desire to treat each of the flows in a certain manner. In response to a same DSCP, all flows corresponding to that DSCP are considered a type of network traffic by class and the traffic in that class gets a particular level of priority in its routing treatment. Note also that the current 6-bit DSCP is considered to be an implementation of a so-called per hop behavior (“PHB”), that is, in layer 3, it is desired for certain multiple flow packets to have a certain behavior, which typically is a quantifiable performance measure such as end-to-end delay. Thus, DSCP is an implementation tool to achieve behavior at layer 3. Lastly, note that differentiated services avoid simple priority tagging and depend on more complex policy or rule statements to determine how to forward a given network packet, and it is more flexible and more scaleable than the routing available to integrated services.
By way of additional background, note that QoS in the form of layer 3 DSCP has in some instances in the prior art been mapped to layer 2 by individual routers. Under such an approach, each such router is given autonomy to provide a relationship between the layer 3 DSCP and a layer 2 priority, thereby attempting to achieve a QoS in layer 2 based on the layer 3 DSCP. However, while such an approach is workable in some implementations, the present inventors have discovered that such an approach also provides drawbacks. Specifically, this prior art approach may provide inconsistent, or at least different, QoS treatments by individual routers based upon the manner in which they implement mapping. Further, such an approach generally provides only a relatively localized effect at each location of an individually-mapping router. In contrast and as detailed later, the preferred embodiments are directed to providing consistent mapping between layers, such as between layer 3 DSPC and layer 2, across numerous routers distributed at multiple locations within a network. Further and as appreciated later, when a change in the mapping is desired, that change can be implemented at a single central location and then broadcast to multiple routers, thereby allowing a uniform change at comparable times and at the location of the multiple routers receiving the broadcast.
While the preceding technologies have proven useful in network packet management, the present inventors have discovered that such technologies may be improved. Specifically, the present state of the art typically implements the QoS of differentiated services in connection with the core routers of a network. Thus, the benefits of differentiated services are generally realized in a coarse manner at the more central core area of the network. However, it has been determined in connection with the present inventive embodiments that improvements also may be made with respect to the so-called last mile problem, that is, in the prioritizing of packet communications both at and beyond the edge routers of a network, such as in the communication at a local area network connected to an edge router. In addition, the present inventors have recognized that as networks and network complexity increase, there is a need for greater consistency in QoS and behavior control across larger portions of the network. Indeed, as the number of different behaviors and/or DSCPs at each layer increases, the need for consistency in traffic treatment is even greater. Thus, there arises a need to expand certain benefits of the prior art while addressing the last-mile problem and the increasing demands on QoS, as is accomplished by the preferred embodiments described below.